An image captured by a camera often appears with purple fringing owing to the sensing of infrared by a sensor in an optical lens module of the camera. Generally, an infrared cut-off filter can effectively block infrared having a wavelength ranging from 700 nm to 1100 nm. However, light leakage may happen for infrared having a wavelength greater than 1100 nm. Moreover, with larger incident angle, the wavelength of the incident infrared may be reduced owing to blue shift effect, so that the purple fringing problem becomes worse.